Bicolor? - Page 13

Right, but it sounds like you're assuming it comes from another loci, which for the reasons I've stated (in #2) is very unlikely;

The quote you gave in 2) actually confirms that it does come from other loci. -

2) "Besides Agouti and Mc1r, mutations in at least 10 additional genes can interfere with the switching of pigment type."

And a quote I gave earlier -

but in very few instances has it been possible
to distinguish allelic variation at Agouti from darkening
due to modifier genes distinct from Agouti and
Mc1r."

What both of these quotes are saying is that other genes (loci) are responsible for some of the variation in pigment types. 

I don't understand why you are disputing this Daryl, when the A locus alleles have already been defined by the researchers working on this.

Are you being condescending?  Yes, I know the difference between a locus and an allele.  "Gene" can be a very misleading term though.

Are you still assuming there are only a few allele types that make up a complete compliment?  Sable alleles from one family for example are not necessarily to be assumed identical to the sable alleles of another, as I've already stated.  These are not basic elements.

Your questions aren't very clear to me, so it's difficult to interpret what you think I know (or don't know), versus what you want to know (or already know).  It seems as if you're trying to identify a difference in the structure of the dna, when most likely the answer lies in both the structure and also the process in how that dna will be determined to express itself.

Are you being condescending?

No, I genuinely believe there are gaps in your understanding of basic genetics.


Are you still assuming there are only a few allele types that make up a complete compliment? Sable alleles from one family for example are not necessarily to be assumed identical to the sable alleles of another, as I've already stated. These are not basic elements.

Sorry Daryl, but this is nonsense.  There are just two sable alleles - A^y true sable and a^w wolf sable, and it is just a^w - wolf sable we are dealing with in the GSD (though A^y may occur at low frequency).

In all the years of colour research, dating back to the 1930s (IIRC), there has never been a proposal for addtional sable alleles, and if there were any in existence, I'm sure the modern day DNA researchers would be aware of them. 

Of course there are differing expressions of sable and this is where the modifying genes come in (in addition to co-dominance), and yes, these modifiers can be specific to families, just as any genes can.

I know I've posted this many time, but please read this page on the website of the lab at the forefront of this -  http://homepage.usask.ca/~schmutz/agouti.html

Another reference to the effects of modifiers on sable -

The observations that variable amounts of sable
markings can be present in dogs carrying either an ay
or an aw allele suggests that variation is due to
modifier genes and is consistent with studies in
laboratory mice in which different inbred strains
carrying the ay allele exhibit different degrees of
darkening (Lamoreux and Galbraith 1986; Suto and
Sekikawa 2003).

http://www.gdca.org/Fawnsable.pdf

In all the years of colour research, dating back to the 1930s (IIRC), there has never been a proposal for addtional sable alleles, and if there were any in existence, I'm sure the modern day DNA researchers would be aware of them.

In mice there are 17 agouti alleles described here , some of them are clearly versions of sable (assuming you mean banded hairs).

The observations that variable amounts of sable
markings can be present in dogs carrying either an ay
or an aw allele suggests that variation is due to
modifier genes.....

A suggestion is not a confirmation.  But yes, modifier genes DO affect some differences in phenotype, but are not responsible for the bicolor phenotype.

I don't understand why you are disputing this Daryl

Truth is, I didn't realize I was disputing anything with you, until the last couple posts.  I'm not so much interested in pushing the idea that there's so many different forms of agouti allele types, as I am suggesting there are complex processes that regulate their expression.  These processes offer an alternative explanation for bicolor transference to offspring in place of the "suggested modifier genes", and keeping in line with the current tested and proven model for inheritance.

Since you don't like my nonsense, I'll happily abandon this discussion.

Sorry if I've been offensive Daryl, but I think I'll agree, it's best to leave this discussion as it is :)

As we know, saddlebacked patterns are not very common among workinglines, although blanketbacked patterns are more prevalent.

Examining the color genotyping of a workingline pedigree containing the saddle pattern, I'm questioning the validity of my proposal that the blanketback pattern is a greater LOF variant of B&T that is recessive to the saddleback variation in phenotypical expresssion.  Blanketback expression seems to rely on modifiers outside the agouti locus acting on the B&T allele.

Case in point would be Taz vom True Haus, a blanketback whose mother was a saddleback (from nice workinglines!).
http://www.pedigreedatabase.com/german_shepherd_dog/pedigree/609556.html
http://www.truehaus.com/taz.htm
This all depends on the assumption that his sire Tom vom haus Pixner carries recessive black, based on only one example of black progeny I can find listed in this database.  If Tom isn't really black factored, then my original proposal may still hold true.

Guess I forgot to explain, Taz's maternal grandmother Hajen O'Sunske is a saddleback dog who came from two blanketbacked dogs.  So, that alone implies that saddleback is not dominant to blanketback.

Daryl, I don't understand how you draw that conclusion.

If you consider blanketback to be the phenotypical appearance of a genotype saddle with a black recessive [or saddle with bicolor recessive (or, if you like saddle/saddle+modifier)], then you will get blacks and blanket backs and saddle backs.

So,

presumptively, from your example:

Boban: saddle/black
Hajen: saddle/black

Cayenne= saddle/saddle

I'm not clear what conclusion you think I've drawn.  What I originally proposed was that saddle was dominant to blanket, so if a genotype of saddle/blanket was present, the dog would be a saddle phenotype.  Hajen O'Sunske appearantly disproves that, and suggests that modifiers outside of the agouti locus are necessary for the blanket phenotype of a black & tan carrier.  The reason she disproves that, is because if either of her blanketbacked parents were carriers of saddle pattern, they would phenotypically display that.